Our previous studies have indicated that the direction of blood flow in the anterior ciliary arteries is from inside the eye to the outside contrary to the generally accepted pattern from outside of the eye to the inside. Under these circumstances, the flow of blood in anterior ciliary arteries therefore could be under the control of the intracular pressure. Since the anterior ciliary anterial supply of blood is to the drainage area of the anterior chamber, including the canal of Schlemm, interference with blood supply to this area could be produced by increases in ocular pressure. This study proposes to study several vascular parameters of the anterior ciliary vessels including measurement of blood flow by Doppler laser velocimetry, measurement of episcleral pressures, the diameters of the episcleral vessels and the concentration of oxygenated and reduced hemoglobin in the episcleral vessels by photographic means. Changes in these measurements will be determined in subjects with increased ocular pressure, and in those in which acute and chronic increases of ocular pressure are produced. Similarly, subjects whose ocular pressures have been decreased by surgery, laser treatment or drugs will also be studied both on an acute and chronic basis. In addition, the effect of systemic vascular pressure on the circulation of the anterior ciliary vessels will be studied with subjects who have normal ocular pressure but whose vascular pressure is elevated or is to be treated by blood pressure lowering drugs. These studies will therefore document changes in the anterior ciliary circulatory dynamics in relation to ocular pressure and systemic vascular pressure and may provide insight as to changes in the vascular supply to the anterior segment of the eye in glaucoma.